517 Background: Neoadjuvant endocrine therapy has shown efficacy in hormone-responsive postmenopausal breast cancer patients. We aimed to assess the efficacy and safety of cytotoxic chemotherapy versus endocrine therapy for hormone-responsive lymph node-positive premenopausal breast cancer patients in a neoadjuvant setting. (NCT01622361). Methods: In this phase 3, randomized, double blind, parallel group, multicenter study, we enrolled premenopausal women with estrogen receptor (ER)-positive, HER2-negative, and lymph node-positive premenopausal breast cancer patients. Patients were randomized to either 24 weeks of neoadjuvant chemotherapy with adriamycin plus cyclophosphamide (AC) followed by taxane (T) or neoadjuvant endocrine therapy with zoladex and tamoxifen. Results: 187 patients were randomly assigned to chemotherapy (n=95) or endocrine therapy (n=92), and 174 patients completed the 24 week neoadjuvant treatment period (n=87, both). More patients in the chemotherapy group had a complete or partial response than did those in endocrine therapy arm on both caliper (chemotherapy 83.9% vs endocrine therapy 71.3%, OR 0.476 95% CI 0.228 to 0.994) and MRI (chemotherapy 83.7% vs endocrine therapy 52.9%, OR 0.219, 95% CI 0.107 to 0.447). Three patient on chemotherapy group (3.4%) and 1 patients (1.15%) on endocrine treatment group showed complete pathologic response. In the patients who had breast cancer with low Ki 67 expression (<20%) on initial biopsy, clinical response on caliper were shown similar on both treatment group (HR 0.958, 95%CI 0.296 to 3.101). Five patients who had no tumor on the breast or lymph node after 24 week neoadjuvant endocrine therapy had higher ER score (all allred score >6), all low grade (1or 2) low Ki 67(≤20%) expression (4/5 patients) on initial biopsy specimen. Conclusions: In premenopausal breast cancer patients, 24 weeks neoadjuvant chemotherapy showed better clinical response than endocrine therapy. Low Ki 67 expression could be a parameter of the endocrine treatment. Clinical trial information: NCT01622361.
Breast Cancer Index and prediction of benefit from extended endocrine therapy in breast cancer patients treated in the Adjuvant Tamoxifen—To Offer More? (aTTom) trial
